There is disclosed in DE-B-2 045 929, a multipath lifting valve of the type outlined above, which is operated by electrical drive means and which is only force-balanced in its end positions, that is to say in its closure positions, but not in its intermediate positions, so that in these positions, the valve consumes increased electrical power, in order to ensure its reliable operation because of the unbalanced force relationship. Also, the ring seals which are necessarily provided between the valve shaft and the housing of the valve, produce relatively high frictional resistance between these components, which also adds to the power consumed by the drive means, a significant disadvantage in miniature valves. Further, the through-flow capacity of the valve is relative small, since the valve can only be operated under limited pressure and with limited flow cross-sections.
A further force-balanced lifting valve is described in the GB-A-2 164 423. This valve has only an open-shut facility in respect of a single valve opening, and its closure position is force-balanced by means of a piston, which is acted upon by the pressure fluid against a valve disc. A force acts on the force-balancing piston of the valve in the open position of the valve disc, so that correspondingly high power is required of the valve drive means, in order to keep the valve in its open position. Also, because complicated subsidiary flow paths are provided in the valve disc for the pressure fluid flowing to the balancing piston, the cost of manufacturing the valve disc is substantial.
DE-B-1 082 785 discloses a further force-balanced lifting valve having only a single valve opening, and which is force-balanced in its two end positions. The overall design and in particular the construction of its valve body render it unsuitable for use in installations with miniaturised switching components.